docs: def cells():
      '''
      # Slow
      '''
  
      import time
  
      def query_db():
          time.sleep(5)
          return [1, 2, 3, 4, 5]
  
      def clean(data):
          time.sleep(2)
          return [x for x in data if x % 2 == 0]
  
      def myfilter(data):
          time.sleep(2)
          return [x for x in data if x >= 3]
  
      '''
      '''
  
      rows = query_db()
  
      '''
      '''
  
      data = clean(rows)
  
      '''
      '''
  
      data, len(data)